<SEC-DOCUMENT>0001193125-24-239740-index.html : 20241018
<SEC-HEADER>0001193125-24-239740.hdr.sgml : 20241018
<ACCEPTANCE-DATETIME>20241018181056
ACCESSION NUMBER:		0001193125-24-239740
CONFORMED SUBMISSION TYPE:	SC 13G
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20241018
DATE AS OF CHANGE:		20241018

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Upstream Bio, Inc.
		CENTRAL INDEX KEY:			0002022626
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-94651
		FILM NUMBER:		241381615

	BUSINESS ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		781-208-2466

	MAIL ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			BCLS Fund III Investments, LP
		CENTRAL INDEX KEY:			0001952107
		ORGANIZATION NAME:           	
		IRS NUMBER:				873064173
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G

	BUSINESS ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6175162000

	MAIL ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13G
<SEQUENCE>1
<FILENAME>d814421dsc13g.htm
<DESCRIPTION>SC 13G
<TEXT>
Document 1 - file: d814421dsc13g.htm

</DOCUMENT>
</SEC-DOCUMENT>